Formulations strategies for biopharmaceuticals--ensuring success to market.

It was clear from the number of attendees and the broad spectrum of organizations represented at this conference, that effective formulation development for biopharmaceuticals is a critical and timely issue. From DNA-based products to antibodies, vaccines to therapeutics, administered by every route known to medicine, formulation plays a critical role in the ultimate success of biopharmaceutical products. It was obvious from the various case studies presented that effective formulation development is not often achieved as an organization enters into drug development. In fact, systematic pre-formulation work was stressed by most speakers as an effective use of company resources. In order to develop successful formulations, it is essential that appropriate analytical information is collected, that excipients are systematically evaluated, and that the developer understands the basis of stability of the drug product. In all cases, this means understanding product instability, including the physicochemical and thermodynamic basis for instability. Drugs such as therapeutic antibodies, which may require large doses to achieve the desired pharmacological effect, require ever more advanced formulation development to achieve concentrations in the 100-mg/ml range. Potent drugs, such as gene therapies and DNA vaccines, require formulation development in order to achieve effective delivery and expression. On aggregate, it is apparent that there is much to learn in formulation development, from each other as well as in the unexplored territory ahead. This conference provided an excellent forum for the exchange of ideas and information regarding effective formulation development for biopharmaceuticals.

Endocytosis and nuclear trafficking of adeno-associated virus type 2 are controlled by rac1 and phosphatidylinositol-3 kinase activation.

Adeno-associated virus (AAV) is a single-stranded DNA parvovirus that causes no currently known pathology in humans. Despite the fact that this virus is of increasing interest to molecular medicine as a vector for gene delivery, relatively little is known about the cellular mechanisms controlling infection. In this study, we have examined endocytic and intracellular trafficking of AAV-2 using fluorescent (Cy3)-conjugated viral particles and molecular techniques. Our results demonstrate that internalization of heparan sulfate proteoglycan-bound AAV-2 requires alphaVbeta5 integrin and activation of the small GTP-binding protein Rac1. Following endocytosis, activation of a phosphatidylinositol-3 (PI3) kinase pathway was necessary to initiate intracellular movement of AAV-2 to the nucleus via both microfilaments and microtubules. Inhibition of Rac1 using a dominant N17Rac1 mutant led to a decrease in AAV-2-mediated PI3 kinase activation, indicating that Rac1 may act proximal to PI3 kinase during AAV-2 infection. In summary, our results indicate that alphaVbeta5 integrin-mediated endocytosis of AAV-2 occurs through a Rac1 and PI3 kinase activation cascade, which directs viral movement along the cytoskeletal network to the nucleus.

Cation-exchange high-performance liquid chromatography of recombinant adeno-associated virus type 2.

There has been much interest recently in the development of recombinant viruses as vectors for gene therapy applications. We have constructed a recombinant adeno-associated viral (AAV) vector containing the gene encoding CFTR (cystic fibrosis transmembrane chloride regulator). This vector is currently being used in clinical trials as a treatment for cystic fibrosis. In the course of scale-up and process optimization efforts, a variety of analyses have been developed to characterize yield and quality. Although these methods produce quantitative and highly reproducible results, most are very time intensive. For example, a standard bioassay requires a 72-h incubation period followed by an additional day of analysis. Other tests such as UV spectrophotometry are fast, but unable to distinguish between whole virus, free protein, and DNA. Here, we describe an analytical cation-exchange high-performance liquid chromatographic method utilizing a TSKgel SP-NPR strong cation-exchange column. Unlike the bioassay which requires a 96-h wait for information, this method yields data in less than 20 min. In addition to the quick assay turn-around, the material eluting in the single peak was found to be intact, infectious, nuclease resistant AAV particles. This offers a significant advantage over the limited information one gains from UV spectrophotometry. This demonstrates the utility of chromatography for analysis and purification of viral vectors.

American Society of Gene Therapy - Third Annual Meeting.

The field of gene therapy, delivering genes to directly treat diseases, has had a remarkable year. This is no more evident than in the scope of the third annual meeting of the American Society of Gene Therapy (ASGT). Clear progress has been made in both ex vivo clinical protocols and in vivo administration. The meeting covered every major method of gene delivery, from injection of naked DNA to advanced synthetic gene delivery systems, as well as the major viral-based vectors. The optimism of the society was tempered, however, by the much-publicized death of a patient in a clinical trial at the University of Pennsylvania last year. There was a correspondingly high regulatory presence at the meeting, with several presentations by representatives of the US FDA and National Institutes of Health (NIH). Major clinical advances in gene therapy have been in genetic diseases, including hemophilia, severe combined immunodeficiency, and cystic fibrosis. Therapies are in later-stage clinical trials, and evidence of efficacy has been demonstrated, most notably by the apparent cure of SCID-affected children in Paris by ex vivo gene therapy with cytokine receptor subunit genes. Cancer gene therapy is also making significant headway, with many products entering phase II and III trials. Basic technology development is proceeding in vector targeting, enhancement of gene transfer efficiency, and regulating expression of therapeutic genes. In addition, basic research demonstrates the promise of new combined modes for treating diseases such as muscular dystrophy, lysosomal storage diseases and cardiovascular disease.

Process and product development in the manufacturing of molecular therapeutics.

In the development of molecular therapies, a great deal of attention has focused on tissue targets, gene delivery vectors, and expression cassettes. In order to become an approved therapy, however, a molecular therapeutic has to pass down the same product registration pathway as any other biological product. Moving from research into industrial production requires careful attention to regulatory, manufacturing and quality concerns. Early work on developing and characterizing robust and scaleable manufacturing processes will ultimately be rewarded by ease of implementation as the product is successful in clinical trials. Regulatory agencies require solid process and product characterization studies to demonstrate control and understanding of the molecular therapeutic. As the gene therapy industry matures, standards will continue to rise, creating an industry that is capable of producing safe, high-quality and effective therapies for many of the world's most difficult disease targets.

Process and product development in the manufacturing of molecular therapeutics.

In the development of molecular therapies, a great deal of attention has focused on tissue targets, gene delivery vectors, and expression cassettes. In order to become an approved therapy, however, a molecular therapeutic has to pass down the same product registration pathway as any other biological product. Moving from research into industrial production requires careful attention to regulatory, manufacturing and quality concerns. Early work on developing and characterizing robust and scaleable manufacturing processes will ultimately be rewarded by ease of implementation as the product is successful in clinical trials. Regulatory agencies require solid process and product characterization studies to demonstrate control and understanding of the molecular therapeutic. As the gene therapy industry matures, standards will continue to rise, creating an industry that is capable of producing safe, high-quality and effective therapies for many of the world's most difficult disease targets.

A high-throughput hybridization method for titer determination of viruses and gene therapy vectors.

One of the challenges facing researchers working with viruses and gene therapy vectors is the need to rapidly assay for infectious virus. Current methods used to titer many viruses are cumbersome and are not amenable to handling large numbers of samples. Here we describe the development of an assay that can rapidly quantify infectious viruses and gene therapy vectors. The assay relies on biological amplification of viral sequences and hybridization of labeled probes to immobilized nucleic acid from infected cells. The amplification of the viral genome makes this a highly sensitive method. The assay is configured in a high-throughput format that has been used to detect recombinant adeno-associated virus (AAV), wild-type AAV and infectious adenovirus. The assay is quantitative, and can be used to titer virus preparations with or without a known standard.

Gene transfer using a novel fusion protein, GAL4/invasin.

The delivery of DNA to target cells using simple, defined, nonviral systems has become an area of intense interest in gene therapy. We describe here the development and characterization of one such novel system. A recombinant, bifunctional, fusion protein was expressed and purified from Escherichia coli. This protein consists of the DNA-binding domain of the yeast transcription factor GAL4 fused to the cell binding, internalization domain of the Yersinia pseudotuberculosis inv gene product, invasin. This protein, GAL4/Inv, together with poly-L-lysine, formed complexes with a chloramphenicol acetyltransferase (CAT) reporter plasmid that contains eight repeats of the GAL4 consensus recognition sequence. These complexes were shown to transfect target cells in an invasin receptor-dependent manner, resulting in transient CAT expression. A simple, targeted DNA delivery vehicle, as we describe here, represents a viable approach to nonviral gene delivery.

In vitro sulfotransferase activity of NodH, a nodulation protein of Rhizobium meliloti required for host-specific nodulation.

Early stages of nodulation involve the exchange of signals between the bacterium and the host plant. Bacterial nodulation (nod) genes are required for Rhizobium spp. to synthesize lipooligosaccharide morphogens, termed Nod factors. The common nod genes encode enzymes that synthesize the factor core structure, which is modified by host-specific gene products. Here we show direct in vitro evidence that Rhizobium meliloti NodH, a host-specific nodulation gene, catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate to the terminal 6-O position of Nod factors, and we show substrate requirements for the reaction. Our results indicate that polymerization of the chitooligosaccharide backbone likely precedes sulfation and that sulfation is not absolutely dependent on the presence or the particular structure of the N-acyl modification. NodH sulfation provides a tool for the enzymatic in vitro synthesis of novel Nod factors, or putative Nod factors intermediates, with high specific activity.

Biosynthesis of Rhizobium meliloti lipooligosaccharide Nod factors: NodA is required for an N-acyltransferase activity.

Rhizobium bacteria synthesize N-acylated beta-1,4-N-acetylglucosamine lipooligosaccharides, called Nod factors, which act as morphogenic signal molecules to legume roots during development of nitrogen-fixing nodules. The biosynthesis of Nod factors is genetically dependent upon the nodulation (nod) genes, including the common nod genes nodABC. We used the Rhizobium meliloti NodH sulfotransferase to prepare 35S-labeled oligosaccharides which served as metabolic tracers for Nod enzyme activities. This approach provides a general method for following chitooligosaccharide modifications. We found nodAB-dependent conversion of N-acetylchitotetraose (chitotetraose) monosulfate into hydrophobic compounds which by chromatographic and chemical tests were equivalent to acylated Nod factors. Sequential incubation of labeled intermediates with Escherichia coli containing either NodA or NodB showed that NodB was required before NodA during Nod factor biosynthesis. The acylation activity was sensitive to oligosaccharide chain length, with chitotetraose serving as a better substrate than chitobiose or chitotriose. We constructed a putative Nod factor intermediate, GlcN-beta 1,4-(GlcNAc)3, by enzymatic synthesis and labeled it by NodH-mediated sulfation to create a specific metabolic probe. Acylation of this oligosaccharide required only NodA. These results confirm previous reports that NodB is an N-deacetylase and suggest that NodA is an N-acyltransferase.

Homology of Rhizobium meliloti NodC to polysaccharide polymerizing enzymes.

Rhizobium bacteria form nitrogen-fixing nodules on legume roots. As part of the nodulation process, they secrete Nod factors that are beta-1,4-linked oligomers of N-acetylglucosamine. These factors depend on nodulation (nod) genes, but most aspects of factor synthesis are not yet known. We show here that one gene, nodC, shows striking similarity to genes encoding proteins known to be involved in polysaccharide synthesis in yeast and bacteria, specifically chitin and cellulose synthases, as well as a protein with unknown function in Xenopus embryos, DG42. This similarity is consistent with a role for the NodC protein in the formation of the beta-1,4-linkage in Nod factors.

Depolarization of alfalfa root hair membrane potential by Rhizobium meliloti Nod factors.

Although much is known about the bacterial genetics of early nodulation, little is known about the plant cell response. Alfalfa root hair cells were impaled with intracellular microelectrodes to measure a membrane potential depolarizing activity in Rhizobium meliloti cell-free filtrates, a plant response dependent on the bacterial nodulation genes. The depolarization was desensitized by repeated exposure to factors and was not observed in a representative nonlegume. A purified extracellular Nod factor, NodRm-IV(S), caused membrane potential depolarization at nanomolar concentrations. This rapid single-cell assay provides a tool for dissecting the mechanisms of host cell response in early nodulation.

Changes in proteinase and peptidase activities during reticulocyte maturation.

The ability of rabbit reticulocytes to degrade puromycin-peptides and aminoethylcysteine-induced aberrant polypeptides decreased during cellular maturation. Cell-free studies indicate that the fall in proteolytic activity is not a consequence of accumulation of proteinase inhibitors or the conversion of all of the abnormal protein into undegradable forms. A decrease in peptidase activity using seven dipeptides and one tripeptide as substrates was also found to accompany reticulocyte maturation. Addition of the aminopeptidase B inhibitor bestatin to reticulocyte extracts did not inhibit the conversion of acid-precipitable puromycin-peptides to acid-soluble products; bestatin did induce the accumulation of very low molecular weight material (possibly di- or tripeptides) within the acid soluble fraction.

Subcellular distribution of abnormal proteins in rabbit reticulocytes. Effects of cellular maturation, phenylhydrazine and inhibitors of ATP synthesis.

Inhibitors of ATP synthesis (cyanide, dinitrophenol, fluoride) inhibited proteolysis of pulse-labelled abnormal proteins in rabbit reticulocytes and caused an accumulation of the aberrant polypeptides in the cell debris fraction in a manner analogous to phenylhydrazine-induced Heinz bodies. When the reticulocytes were separated into age-groups by sedimentation through discontinuous gradients of bovine serum albumin, the ability of the cells to degrade puromycin peptides decreased with increasing cellular maturity and, in the more mature cells, up to 40% of the labelled abnormal polypeptide remained associated with the cell debris fraction at the end of the chase period. It is suggested that the association of the abnormal polypeptide with the cell debris fraction is a consequence of a maturation-induced loss, or an inhibitor-induced inactivation of the cellular proteolytic activity.

Protease and peptidase activities during reticulocyte maturation.

Rabbit reticulocytes were fractionated according to buoyant density on albumin gradients. The properties of fractionated cells were consistent with the thesis that the procedure separated the reticulocytes according to their degree of maturation. Catabolism of aminoethylcysteine-induced abnormal protein and puromycin-peptides declined with increasing cellular maturity. Cell-free extracts showed a similar decrease in degradative activity: addition of extracts of young cells stimulated proteolysis in extracts from old cells. Peptidase activity also declined during maturation. In the more mature cells abnormal protein was located increasingly in the cell-debris fraction, analogous to Heinz bodies.

Selective proteolysis of abnormal proteins of shortened chain length in rabbit reticulocytes.

Proteolysis of certain shortened globin chains can proceed in cell-free extracts of rabbit reticulocytes in the absence of ATP. Proteolysis of amino acid analogue-induced abnormal globin chains of normal chain length may be stimulated by ATP, however. The ATP independent degradation of globin cyanogen bromide-peptides appears to require the presence of free, unblocked amino groups in the substrate, has a pH optimum of 7.8 and is inhibited by phenanthroline, cobalt and zinc ions, N-ethylmaleimide and cystamine.

Purification and some properties of malarial pigment.

Malarial pigment from erythrocytes infected with Plasmodium berghei was purified by treatment with sodium dodecyl sulphate solution, followed by incubation with Pancreatin. The purified pigment retained the apparently crystalline form of pigment within the parasite, rotated polarised light and had the same solubility characterisation as crude malarial pigment. It contained about 1% iron, all of which could be accounted for in terms of haemin. The iron of the pigment molecule is oxidised by the parasite to the ferric state.